U.S. patent application number 09/861866 was filed with the patent office on 2002-11-28 for dual technology occupancy sensor and method for using the same.
Invention is credited to Baldwin, John R..
Application Number | 20020175815 09/861866 |
Document ID | / |
Family ID | 32736732 |
Filed Date | 2002-11-28 |
United States Patent
Application |
20020175815 |
Kind Code |
A1 |
Baldwin, John R. |
November 28, 2002 |
Dual technology occupancy sensor and method for using the same
Abstract
A dual technology motion or occupancy sensor, and a method for
using the same, to control a lighting circuit to activate and
deactivate lights in a monitored area. The sensor employs an
infrared energy sensor, a microwave energy sensor, and a
controller. The infrared energy sensor outputs an infrared energy
detection signal indicative of detection or non-detection of
infrared energy, and the microwave energy sensor outputs a
microwave energy detection signal indicative of detection or
non-detection of microwave energy. The controller outputs a control
signal to control activation and deactivation of the lighting
circuit in response to a condition of the infrared energy detection
signal and a condition of the microwave energy detection signal.
Specifically, the controller activates the lighting circuit to turn
on the lights in the monitored area when the infrared energy
detection signal and microwave energy detection signal indicate
occupancy or motion in the monitored area, and maintains the lights
in the active state as long as either the microwave energy sensor
or the infrared energy sensor sense occupancy or motion in the
monitored area.
Inventors: |
Baldwin, John R.; (Newtown,
CT) |
Correspondence
Address: |
Joseph J. Buczynski
Roylance, Abrams, Berdo & Goodman, L.L.P.
1300 19th Street, N.W., Suite 600
Washington
DC
20036
US
|
Family ID: |
32736732 |
Appl. No.: |
09/861866 |
Filed: |
May 22, 2001 |
Current U.S.
Class: |
340/567 ;
250/221 |
Current CPC
Class: |
G01S 13/86 20130101;
H05B 47/13 20200101; G08B 29/183 20130101; G01S 13/04 20130101;
Y02B 20/40 20130101; G08B 13/1645 20130101 |
Class at
Publication: |
340/567 ;
250/221 |
International
Class: |
G08B 013/18 |
Claims
What is claimed is:
1. A sensor, adapted to control a lighting circuit, comprising: an
infrared energy sensor, adapted to output an infrared energy
detection signal indicative of detection or non-detection of
infrared energy; a microwave energy sensor, adapted to output a
microwave energy detection signal indicative of detection or
non-detection of microwave energy; and a controller, adapted to
output a control signal to control activation and deactivation of
said lighting circuit in response to a condition of said infrared
energy detection signal and a condition of said microwave energy
detection signal.
2. A sensor as claimed in claim 1, wherein: said infrared energy
sensor outputs said infrared energy detection signal having a first
condition representative of detection of said infrared energy, and
outputs said infrared energy detection signal having a second
condition representative of non-detection of said infrared energy;
and said microwave energy sensor outputs said microwave energy
detection signal having a first condition representative of
detection of said microwave energy, and outputs said microwave
energy detection signal having a second condition representative of
non-detection of said microwave energy.
3. A sensor as claimed in claim 2, wherein: when said controller is
outputting said control signal having a deactivation condition to
maintain said lighting circuit in an inactive state, said
controller is adapted to change said control signal to an
activation condition to activate said lighting circuit in response
to said infrared energy detection signal having said first
condition and said microwave energy detection signal having said
first condition.
4. A sensor as claimed in claim 2, wherein: when said controller is
outputting said control signal having an activation condition to
maintain said lighting circuit in an active state, said controller
is adapted to maintain said control signal in said activation
condition to maintain activation of said lighting circuit in
response to said infrared energy detection signal having said first
condition and said microwave energy detection signal having said
second condition, or vice versa.
5. A sensor as claimed in claim 2, wherein: when said controller is
outputting said control signal having an activation condition to
maintain said lighting circuit in an active state, said controller
is adapted to change said control signal to a deactivation
condition to deactivate said lighting circuit in response to said
infrared energy detection signal having said second condition, and
said microwave energy detection signal having said second
condition, for a predetermined duration of time.
6. A sensor as claimed in claim 5, wherein: when either said
infrared energy detection signal or said microwave energy detection
signal fails to maintain its respective said second condition for
said predetermined duration of time, said controller is adapted to
maintain said control signal in said activation condition to
maintain said lighting circuit in said active state.
7. A sensor as claimed in claim 2, wherein: when said controller is
outputting said control signal having an activation condition to
maintain said lighting circuit in an active state, said controller
is adapted to change said control signal to a deactivation
condition to deactivate said lighting circuit in response to said
infrared energy detection signal having said second condition, or
said microwave energy detection signal having said second
condition, for a predetermined duration of time.
8. A sensor as claimed in claim 7, wherein: when either said
infrared energy detection signal or said microwave energy detection
signal fails to maintain its respective said second condition for
said predetermined duration of time, said controller is adapted to
maintain said control signal in said activation condition to
maintain said lighting circuit in said active state.
9. A sensor as claimed in claim 1, wherein: said controller is
adapted to compare a magnitude of said microwave energy detection
signal to a microwave detection threshold to determine detection or
non-detection of microwave energy, and is adapted to compare a
magnitude of said infrared energy detection signal to an infrared
detection threshold to determine detection or non-detection of
infrared energy.
10. A sensor as claimed in claim 9, wherein: said controller is
adapted to adjust at least one of a magnitude of said microwave
detection threshold and a magnitude of said infrared detection
threshold.
11. A method for controlling a lighting circuit, comprising:
detecting for infrared energy in a monitored area and providing an
infrared energy detection signal indicative of detection or
non-detection of said infrared energy; detecting for microwave
energy in said monitored area and providing a microwave energy
detection signal indicative of detection or non-detection of said
microwave energy; and controlling activation and deactivation of
said lighting circuit in response to a condition of said infrared
energy detection signal and a condition of said microwave energy
detection signal.
12. A method as claimed in claim 11, wherein: said infrared energy
detecting step provides said infrared energy detection signal
having a first condition representative of detection of said
infrared energy, and outputs said infrared energy detection signal
having a second condition representative of non-detection of said
infrared energy; and said microwave energy detecting step provides
said microwave energy detection signal having a first condition
representative of detection of said microwave energy, and outputs
said microwave energy detection signal having a second condition
representative of non-detection of said microwave energy.
13. A method as claimed in claim 12, wherein: when said controlling
step is maintaining said lighting circuit in an inactive state,
activating said lighting circuit when said infrared energy
detection signal has said first condition and said microwave energy
detection signal has said first condition.
14. A method as claimed in claim 12, wherein: when said controlling
step is maintaining said lighting circuit in an active state,
maintaining activation of said lighting circuit when said infrared
energy detection signal having said first condition and said
microwave energy detection signal has said second condition, or
vice versa.
15. A method as claimed in claim 12, wherein: when said controlling
step is maintaining said lighting circuit in an active state,
deactivating said lighting circuit when said infrared energy
detection signal has said second condition, and said microwave
energy detection signal has said second condition, for a
predetermined duration of time.
16. A method as claimed in claim 15, wherein: when either said
infrared energy detection signal or said microwave energy detection
signal fails to maintain its respective said second condition for
said predetermined duration of time, maintaining said lighting
circuit in said active state.
17. A method as claimed in claim 12, wherein: when said controlling
step is maintaining said lighting circuit in an active state,
deactivating said lighting circuit when said infrared energy
detection signal has said second condition, or said microwave
energy detection signal has said second condition, for a
predetermined duration of time.
18. A method as claimed in claim 17, wherein: when either said
infrared energy detection signal or said microwave energy detection
signal fails to maintain its respective said second condition for
said predetermined duration of time, maintaining said lighting
circuit in said active state.
19. A method as claimed in claim 11, wherein: said controlling step
compares a magnitude of said microwave energy detection signal to a
microwave detection threshold to determine detection or
non-detection of microwave energy, and compares a magnitude of said
infrared energy detection signal to an infrared detection threshold
to determine detection or non-detection of infrared energy.
20. A method as claimed in claim 19, further comprising: adjusting
at least one of a magnitude of said microwave detection threshold
and a magnitude of said infrared detection threshold.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a sensor device employing
passive infrared and microwave sensor technology, and a method for
using the same. More particularly, the present invention relates to
a method and apparatus employing a motion or occupancy sensor which
includes a passive infrared sensor and microwave sensor in
conjunction with logic circuitry to control activation and
deactivation of devices such as lighting circuits.
[0003] 2. Description of the Related Art
[0004] Motion sensor switches, such as Model 1WS-ZP-M and Model
1WS-ZP-277V motion sensor switches manufactured by Hubbell, Inc.,
include a motion sensor, such as a passive infrared detector (PIR),
and an ambient light level sensor, such as a photocell. Other
motion sensor switches are described in U.S. Pat. Nos. 5,821,642 to
Nishihira et al., 5,699,243 to Eckel et al., and 4,874,962 to
Hermans, the entire contents of each being incorporated herein by
reference.
[0005] Motion sensor switches of this type can be used, for
example, as an occupancy detector which shuts off lights in a room
when the sensor detects that no one is present in the room, and
turns on the lights in the room when a person enters the room. A
motion sensor switch also can be used, for example, as a motion
sensor for an alarm system.
[0006] During operation, the motion sensor of the motion sensor
switch monitors an area, such as an office, conference room in a
building, or a home, for the presence of movement. Specifically,
the motion sensor detects a change in the infrared energy radiating
from regions in the area monitored by different sensing lobes of
the PIR detector, which generally have a pass band within the 8-14
.mu.m infrared range. If a person enters the monitored area, the
person changes the amount of infrared energy being detected by the
PIR detector. Therefore, the magnitude of the signal output by PIR
detector, which is representative of the amount of detected
infrared energy, will change. A motion sensor circuit in the motion
sensor switch processes this signal, and provides a signal to a
controller indicating that the amount of infrared energy received
by the infrared detector has changed.
[0007] The controller interprets the signal provided by the motion
sensor circuit, along with the signal provided by ambient light
level sensor. If the signal provided by ambient light level sensor
indicates that the ambient light in the monitored area is low
(e.g., very little natural light is present in the monitored area),
the control circuit will turn on or increase the brightness of the
lights in the monitored area. However, if the signal provided by
ambient light level sensor indicates that the ambient light in the
monitored area is sufficient (e.g., due to sunlight, etc.), the
control circuit may not turn on or brighten the lights, or may only
brighten the lights slightly. In either event, control of the
lights is based on the signals provided by the motion sensor and
ambient light level sensor.
[0008] Motion sensor switches of this type also typically include a
delay timing adjustment device, such as a potentiometer, which can
be manually adjusted to set the delay time during which the lights
should remain on after all occupants have left the monitored area.
For example, if the delay timing adjustment device is adjusted to a
30-second setting, when all occupants leave and remain out of the
monitored area for a period of time exceeding 30 seconds, the
circuit of the motion sensor turns off the lighting load in the
monitored area to conserve energy.
[0009] The motion sensor switches described above which employ only
a PIR detector are generally suitable for their intended purpose.
However, because PIR detectors detect infrared energy, these types
of sensors can be susceptible to false triggering by other devices
in the monitored area, such as computers, heating vents, and the
like, that emit infrared energy.
[0010] In an attempt to minimize these false triggerings, a sensor
has been developed that uses a PIR detector in conjunction with an
ultrasonic detector. An example of a sensor employing PIR and
ultrasonic detector technologies is described in U.S. Pat. No.
5,189,393 to Hu, the entire content of which is incorporated herein
by reference. As can be appreciated by one skilled in the art, an
ultrasonic sensor detects movement of an object. Accordingly, a
sensor employing a PIR detector and an ultrasonic detector can
include logic circuitry which requires detection of heat and
movement in the monitored area to provide a switching signal to,
for example, activate a lighting circuit.
[0011] Although a sensor employing both PIR and ultrasonic detector
technology may be more accurate than a sensor employing only a PIR
detector or only an ultrasonic detector, this type of sensor does
have certain disadvantages. For example, ultrasonic detectors are
sensitive to air movements such as air turbulence. Therefore, if a
sensor employing an ultrasonic detector is used to monitor a room
in a building, the air flow from the ventilation system of the
building can cause a false triggering of the detector. Moreover,
ultrasonic detectors are also sensitive to acoustic noise. Hence,
noisy vehicles such as street sweepers and the like operating
outside the building can cause false triggering of the ultrasonic
detectors in the sensors in the building.
[0012] Other types of dual technology sensors are known for use in
burglar alarm systems. For example, a Sentrol.TM. Model 2T40 motion
sensor employs a microwave sensor technology, such as microwave
impulse radar (MIR) technology and PIR technology. However,
although it is necessary for these types of burglar alarm systems
to accurately detect when an intruder has initially entered a
monitored area to signal an alarm, it is not necessary for these
types of systems to detect with extreme accuracy the continued
presence of the intruder in the monitored area, or to detect when
the intruder has left the monitored area. Therefore, these types of
detectors have not been employed in conjunction with circuitry
suitable for use as lighting control circuitry.
[0013] Accordingly, a need exists for an improved dual technology
sensor which is capable for use as an efficient and accurate motion
sensor for controlling lighting circuitry and does not suffer from
the disadvantages of conventional sensors.
SUMMARY OF THE INVENTION
[0014] An object of the present invention is to provide an accurate
and reliable dual technology motion or occupancy sensor.
[0015] Another object of the present invention is to provide a
motion or occupancy sensor including a PIR sensor and a microwave
sensor.
[0016] A further object of the present invention is to provide a
method of using a dual technology motion or occupancy sensor, such
as a motion or occupancy sensor including a PIR sensor and a
microwave sensor.
[0017] These and other objects of the present invention are
substantially achieved by providing a sensor and method for
controlling a lighting circuit in a monitored area, employing an
infrared energy sensor, a microwave energy sensor, and a
controller. The infrared energy sensor is adapted to output an
infrared energy detection signal indicative of detection or
non-detection of infrared energy, and the microwave energy sensor
is adapted to output a microwave energy detection signal indicative
of detection or non-detection of microwave energy. The controller
is adapted to output a control signal to control activation and
deactivation of the lighting circuit in response to a condition of
the infrared energy detection signal and a condition of the
microwave energy detection signal.
[0018] Specifically, when the controller is controlling the
lighting circuit to be in an inactive state and determines based on
the infrared energy detection signal and microwave energy detection
signal that the monitored area has become occupied, the controller
activates the lighting circuit to turn the lights in the monitored
area on. The controller maintains the lights in the on condition as
long as the infrared energy detection signal or the microwave
energy detection signal indicate that the monitored area is
occupied. However, when both the infrared energy detection signal
and the microwave energy detection signal indicate to the
controller that the monitored area has been unoccupied for a period
of time, the controller deactivates the lighting circuit to turn
the lights in the monitored area off. The controller can determine
the conditions of the microwave and infrared energy detection
signals as indicating occupancy or vacancy of the monitored area by
comparing the signals to respective threshold levels that the
controller can calibrate as appropriate. The controller can also be
configured to deactivate the lighting circuit that is in the active
state when either the microwave energy detection signal or the
infrared energy detection signal fails to indicate detection of
occupancy in the monitored area for a period of time. The
controller can also perform filtering on the microwave and infrared
energy signals to avoid erroneous occupancy detection.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] These and other objects, advantages and novel features of
the invention will be more readily appreciated from the following
detail description when read in conjunction with the accompanying
drawings, in which:
[0020] FIG. 1 is a conceptual block diagram of a dual technology
motion or occupancy sensor according to an embodiment of the
present invention; and
[0021] FIG. 2 is a graph showing an example of operation of a
controller of the dual technology sensor shown in FIG. 1 in
response to conditions of detection signals provided by the PIR
sensor and microwave sensor of the dual technology sensor.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] FIG. 1 is a functional block diagram of a dual technology
sensor 100 according to an embodiment of the present invention. The
dual technology sensor 100 employs a microwave emitter 102 and a
microwave sensor 104 in conjunction with a passive infrared (PIR)
pryoelectric sensor 106 to function as a reliable occupancy
sensor.
[0023] As described in more detail below, the sensor 100 includes a
microcontroller 108, such as a PIC16C microcontroller or the like,
that processes signals representative of the microwave and infrared
energy detected by the microwave sensor 104 and PIR sensor 106,
respectively, to determine occupancy of a monitored area. The PIR
sensor 106 in this example includes an above normal number of
optical fields of view (FOV) and a higher than normal gain because
microcontroller 108 can intelligently decide the validity of a
signal received on its input channel dedicated to the PIR sensor
106. That is, a typical wall mounted PIR sensor will have one layer
of fields of view. However, the PIR sensor 106 employed in sensor
100 will have multiple layers of fields of view. Also, the
microcontroller 108 and its associated circuitry can intelligently
extract signals from noise using various types of signal processing
techniques, such as digital filtering, pattern recognition,
frequency component recognition and the like.
[0024] In this example, the PIR sensor 106 is coupled to analog
circuitry 110 that provides analog signals to the microcontroller
108 in response to detection by the PIR sensor 106 of infrared
energy emitted by an object of interest, such as a person, in the
monitored area. Furthermore, the microwave emitter 102 is driven by
drive circuitry 112 that is coupled to and controlled by the
microcontroller 108 to drive the microwave emitter 102 to emit
microwave energy into the monitored area. The microcontroller 108
can control the drive circuitry 112 to drive the microwave emitter
102 to emit microwave energy either continuously or in pulses each
having a duration of one or several milliseconds. The microwave
sensor 104 is coupled to analog circuitry 114 that provides analog
signal to the microcontroller 108 in response to detection by the
microwave sensor 104 of any microwave energy emitted by the
microwave emitter 102 that has reflected off of an object of
interest, such as a person, in the monitored area. That is, when
the microwave emitter 102 is operating in either the continuous or
pulsed mode described above, the microwave sensor 104 will detect
the Doppler signals reflected off the object of interest.
[0025] As further shown in FIG. 1, sensor 100 includes a microwave
sensitivity adjustment circuit 116 that is coupled to
microcontroller 108 and is operable to adjust the sensitivity of
the microwave detection features of the microcontroller 108 as
described in more detail below. Microcontroller 108 also includes a
PIR digital signal processing component 118, a PIR threshold to
peak noise ratio optimizer component 120, a microwave digital
signal processing component 122, and a microwave threshold to peak
noise ratio optimizer component 124, the purposes and operations of
which are described in more detail below. In addition,
microcontroller 108 is coupled to a relay and relay drive circuit
126 to control switching of the relay to, for example, activate and
deactivate a lighting circuit (not shown).
[0026] The operation of the sensor 100 will now be described with
reference to FIG. 2.
[0027] With the release of the new NEMA WD 7-1999 Occupancy Motion
Sensor Standard, it will become apparent that dual technology
sensors, which operate so that either technology ("OR" logic) will
keep the sensor load in an "on" state, can have significantly
better maintained motion sensor patterns than sensors which employ
only PIR technology. Concerning sensor 100, it is noted that the
use of microwave and PIR technologies for energy management
control, for example, as an occupancy sensor to activate and
deactivate lights in a room during occupancy and unoccupancy,
respectively, is somewhat different from the use of such
technologies in a dual technology security sensor. For example, in
a security sensor application, it is a goal to reduce the number of
false alarms to zero, if possible. Hence, to minimize the
occurrence of false alarms, the logic circuitry is configured as
"AND" logic which requires that both technologies (e.g., PIR and
microwave technologies) must detect a degree of motion sufficient
to produce signals exceeding their individual alarm thresholds, or
which satisfy signal signature comparison criteria, before the
security sensor provides an alarm output.
[0028] On the contrary, false activations of energy management
sensors need not be zero, but simply should be kept low as low as
possible, and particularly never above a level where they are
discernible by, or a problem for, the user. Typically in these
types of applications, it is a more significant problem if the
sensor deactivates the lights in the monitored area when the
monitored area is still occupied. For these reasons, the dual
technology energy management sensor 100 will typically activate the
relay and relay drive circuit 126 to initially activate (i.e., upon
the first detected motion) the lighting circuit when both
technologies indicate the presence of an object which produces
signals exceeding their individual alarm thresholds. It is noted
that instead of comparing the signals to threshold levels, other
signal evaluation techniques can be used, such as signal signature
comparison techniques or other digital signal processing
techniques, to determine whether the signals represent the presence
of an object. However, as discussed in more detail below, to
prevent premature deactivation of the lighting circuit when the
monitored area is still occupied, the microcontroller 108 in sensor
100 will reset its delay timer to zero when either technology (`OR`
logic) detects motion which produces a signal exceeding the alarm
threshold for that technology (or, for example, meeting the signal
signature comparison criteria), thus maintaining the lighting
circuit in an active state to keep the lights on.
[0029] The above conditions can be grouped into three categories,
namely, initial trigger motion detection, maintained mode of
operation, and deactivation when monitored area becomes unoccupied.
The initial trigger motion detection operation will first be
discussed.
[0030] When the microcontroller 108 is controlling the relay and
relay drive circuit 126 to maintain the lighting circuit in an
inactive (off) state, the microcontroller 108 monitors the signals
provided by the PIR detection analog circuitry 110 and microwave
detection analog circuitry 114 and compares those signals to
respective threshold values or signal signatures. The PIR threshold
to peak noise ratio optimizer component 120 and the microwave
threshold to peak noise ratio optimizer component 124 of
microcontroller 108 adjust the threshold to peak noise ratios
(T/N.sub.pk) for the detected PIR energy and microwave energy,
respectively, to provide more accurate threshold comparisons and
thus more optimum performance. Thus, the microwave and PIR
technologies can each have microcontroller determined (T/N.sub.pk)
which are optimized for the type of application in which the sensor
100 is employed.
[0031] Moreover, as discussed above, instead of using threshold
techniques, the microcontroller 108 and its associated circuitry
can employ signal signature comparison techniques, or other digital
signal processing techniques, to evaluate the signals to determine
whether the signals representing the PIR energy and microwave
energy have characteristics representative of motion detection. For
example, microcontroller 108 can be configured to evaluate and
reject signals with rise times slower or faster than specified
values. Microwave Doppler signals can also be intelligently
processed using frequency discrimination to reject false microwave
detection signals. Further details of these types of signal
processing techniques that can be performed by microcontroller 108
and its related circuitry and can thus be employed in sensor 100
are described in U.S. Pat. No. 6,151,529 to Thomas J. Batko, the
entire contents of which being incorporated herein by
reference.
[0032] When the microcontroller 108 determines that the level of
signals provided by PIR detection analog circuitry 110 are greater
than their respective threshold level and the signal signature is
correct to represent a valid a PIR signal, microcontroller 108
determines that the PIR sensor 106 has sensed the presence of an
object of interest in the occupied area, which can be referred to
as a "PIR trip" condition. Likewise, when the microcontroller 108
determines that the level of signals provided by microwave
detection analog circuitry 114 are greater than their respective
threshold level and the signal signature is correct to represent a
valid microwave signal, microcontroller 108 determines that the
microwave sensor 104 has sensed the presence of an object of
interest in the occupied area, which can be referred to as a
"microwave trip" condition.
[0033] As discussed briefly above, microcontroller 108 performs an
"AND" logic comparison of the detection result from the PIR sensor
signals and the detection result from the microwave sensor signals
to determine whether to switch the relay and relay drive circuit
126 to activate the lighting circuit. That is, as shown in FIG. 2,
if the signals provided from analog circuitry 110 indicate that the
PIR sensor 106 has detected PIR energy in the occupied area but the
signals provided from analog circuitry 114 indicate that the
microwave sensor 104 has not detected a sufficient level of
reflected microwave signals, or vice versa, controller 108 will
maintain the relay and relay drive circuit 126 in the "inactive"
state that therefore maintains the lighting circuit in an inactive
state. The lights in the monitored area therefore remain off.
[0034] However, when microcontroller 108 determines that the
signals provided from analog circuitry 110 indicate that the PIR
sensor 106 has detected PIR energy in the occupied area, and
signals provided from analog circuitry 114 concurrently or nearly
concurrently with the signals from analog circuitry 110 indicate
that the microwave sensor 104 has detected a sufficient level of
reflected microwave signals, microcontroller 108 will start a delay
timer to begin counting, and will control the relay drive circuit
126 to place the relay in the "active" state that therefore
switches the lighting circuit to an active state and turns the
lights in the monitored area "on". It is also noted that the
microcontroller 108 can be configured to accept microwave sensor
signals as indicative of motion or occupancy detection if they are
in time coincidence or substantially in time coincidence with the
PIR sensor signals indicating motion or occupancy detection.
[0035] When the microcontroller 108 is controlling the relay and
relay drive circuit 126 to maintain the lighting circuit in an
active (on) state, the microcontroller 108 monitors the signals
provided by the PIR detection analog circuitry 110 and microwave
detection analog circuitry 114 and compares those signals to
respective threshold values. Alternatively, the microcontroller 108
and its related circuitry can evaluate the characteristics of the
signals from the PIR detection analog circuitry 110 and microwave
detection analog circuitry 114 using signal signature comparison
techniques or other digital signal processing techniques as
discussed above and as described in U.S. Pat. No. 6,151,529
referenced above. As discussed briefly above, microcontroller 108
performs an "OR" logic comparison of the detection result from the
PIR sensor signals and the detection result from the microwave
sensor signals to determine whether to keep the relay and relay
drive circuit 126 activating the lighting circuit and to reset the
delay time to zero.
[0036] That is, as shown in FIG. 2, if the signals provided from
analog circuitry 110 indicate that the PIR sensor 106 has detected
PIR energy in the occupied area but the signals provided from
analog circuitry 114 indicate that the microwave sensor 104 has not
detected a sufficient level of reflected microwave signals, or vice
versa, controller 108 will reset its delay timer to zero and start
the delay timer to begin counting again, to maintain the relay and
relay drive circuit 126 in the "active" state, which therefore
maintains the lighting circuit in an active state. The lights in
the monitored area thus remain on.
[0037] As further discussed briefly above, microcontroller 108
performs an "AND" logic comparison of the detection result from the
PIR sensor signals and the detection result from the microwave
sensor signals to determine whether to switch the relay and relay
drive circuit 126 to deactivate the lighting circuit. That is, as
shown in FIG. 2, if the signals provided from analog circuitry 110
indicate that the PIR sensor 106 has detected insufficient PIR
energy in the occupied area and the signals provided from analog
circuitry 114 indicate that the microwave sensor 104 has not
detected a sufficient level of reflected microwave signals,
microcontroller 108 will begin operation to control the relay drive
circuit 126 to switch the relay back to the "inactive" state that
therefore places the lighting circuit in an inactive state.
Typically, microcontroller 108 will use its delay timer to set a
delay period (e.g., from 15 to 30 minutes, or any other suitable
delay period) from the time at which microcontroller 108 determines
based on the signals provided by analog circuitry 110 and 114 that
the monitored area is unoccupied (i.e., the time that the
microcontroller 108 last receive a signal indicating occupancy from
either analog circuitry 110 or analog circuitry 114 as shown in
FIG. 2) until the time that the microcontroller 108 controls the
relay drive circuit 126 to deactivate the lighting circuit (i.e.,
after the delay period has elapsed). The sensor 100 can include a
switch (not shown) to adjust the delay period as desired.
[0038] The lights in the monitored area therefore will be switched
off after this delay period has elapsed, provided that the
microcontroller 108 does not determine that occupancy has been
detected by the microwave sensor 104 or PIR sensor 106. That is, as
discussed above and shown in FIG. 2, if at any time during this
delay period analog circuitry 110 or 114 provides signals having a
level sufficient to indicate detection of occupancy by the
microwave sensor 104, PIR sensor 106, or both, the microcontroller
108 will reset the delay period to zero, begin counting the delay
period again, and continue to control the relay drive circuit 126
to maintain the lighting circuit in an active state, as shown in
FIG. 2. In this event, the lights will remain on.
[0039] It is noted that motion of persons outside the room
containing the sensor 100, as well as water running in plastic
pipes located in the detection pattern, can cause reflection of the
microwave signals and thus detection of those reflected signals by
the microwave sensor 104. In this event, analog circuitry 114 would
provide detection signals to the microcontroller 108, which can be
of a sufficient level to be interpreted by the microcontroller 108
as indicating occupancy in the monitored area, even though the
monitored area is vacant. To avoid these types of false occupancy
indications, the microwave detection sensitivity should therefore
be adjusted based on, for example, the size of the occupied
area.
[0040] However, because the aspect ratio of the microwave pattern
is fixed, sensitivity generally cannot be optimally adjusted for
all rooms which have a variety of different aspect ratios.
Installation procedures thus typically require "walk testing" to
check for excessive microwave sensitivity. For example, the
installer can press a test button (not shown) on the microwave
sensitivity adjustment circuit 116 to place the sensor 100 in a
test mode, so that the installer can walk where he or she does not
want his or her motion or presence to cause a false occupancy
indication. When the test button is pressed, the microcontroller
108 can allow an exit time followed by a fixed (or adjustable) walk
test time for the installer to walk outside the monitored area.
During this test mode, the microcontroller 108 automatically
adjusts the level of sensitivity at which the microcontroller 108
will interpret microwave detection signals from the analog
circuitry 114 as indicating occupancy in the monitored area. For
example, the microcontroller 108 can adjust (e.g., increase) the
threshold to which the microwave detection signals are compared, so
that any signals having a level less than the adjusted threshold
will be interpreted by the microcontroller 108 as indicative of
non-occupancy. It is further noted that this sensitivity adjustment
will also reduce the amount of false activation of the lighting
circuit caused by motion outside the monitored area.
[0041] The microcontroller 108 can also be configured to time
control the potential microwave "trip" signals (i.e., signals that
have sufficient energy to cause a trip) to reduce false occupancy
detection that may from time to time occur due to the types of
activities described above, such as motion outside the occupied
area and so on, even after the above installation and sensitivity
adjustment process has been performed. This is especially important
during the delay period when the microcontroller 108 has detected
that the monitored area is vacant, and is waiting for the delay
period to elapse without an occupancy detection so that the
microcontroller 108 can control the relay control circuit 126 to
deactivate the lighting circuit.
[0042] Microcontroller 108 could therefore be configured to
increase the threshold to peak noise ratio (T/N.sub.pk) during the
first part (e.g., the first 50%) of the delay period. Hence, the
threshold to which the microwave detection signals provided by
analog circuitry 114 are compared is made higher during this first
half of the delay period than during the second half of the delay
period. The level of the microwave detection signals needed to
cause the microcontroller 108 to indicate occupancy is thus greater
during this first half of the delay period than during the second
half of the delay period. Accordingly, this reduces the likelihood
that an erroneous occupancy detection will occur due to microwave
signal detection during the delay period. Types of signal
processing techniques and adaptive timing techniques are described
in U.S. Pat. No. 6,151,529 referenced above, as well as in U.S.
Pat. Nos. 5,699,243 and 5,640,143, the entire contents of each of
these patents being incorporated herein by reference.
[0043] The accuracy of sensor 100 can further be improved in other
ways. For example, as discussed above, when microcontroller 108
determines that the monitored area is occupied due to maintained
motion or occupancy in the monitored area, microcontroller 108
maintains the lighting circuit in an activated state. As can be
appreciated by one skilled in the art, when sensor 100 is used as a
motion sensor for a security system, microcontroller 108 would not
operate in this maintained motion mode, but rather, would provide
an alarm at the instant motion is detected and not deactivate the
alarm even if the monitored area becomes unoccupied. When used as a
lighting control circuit, however, microcontroller 108 can be
configured to accept or reject microwave Doppler information or, in
other words, intelligently process microwave signals using
frequency discrimination techniques to reject false trip
signals.
[0044] For example, Doppler signal frequencies from a person
walking at normal velocities comprise a spectrum of frequencies
which can be bandpass filtered digitally or by using analog
techniques. A microchip, such as an AN616 microchip PIC
microcontroller for digital signal processing (DSP), can be adapted
to microcontroller 108 and microwave digital signal processing
component 122 to provide a 120 Hz notch filter, 60 Hz notch filter,
or both, to notch filter signals which can cause false microwave
trips, such as radio frequency interference (RFI), fluorescent
lighting signals (e.g., 60 Hz and 120 Hz signals), and so on. DSP
provides much sharper bandpass (notch) filtering than analog
filters. Also, microcontroller 108 can be configured to require
more cycles of Doppler per "burst" and/or more "bursts" of Doppler
before recognizing the detected microwave signals as a valid
indication of occupancy. Likewise, PIR digital signal processing
component 118 can filter unwanted signals caused by RFI, room
temperature changes in the field of view of the PIR sensor 106, and
so on, to improve accuracy.
[0045] In addition, acceptable PIR signals and microwave signals
from moving people can be mapped and the results stored in a memory
(not shown) associated with the microcontroller 108. The
microcontroller 108 can be configured to compare these stored
mapped signals to newly sensed signals, and to reject those signals
which do not meet comparison criteria. Also, a history of the ratio
of microwave trips to PIR trips can be stored in the memory
associated with microcontroller 108. Microcontroller 108 can be
configured to recognize when the ratio of microwave trips to PIR
trips is excessively high or low, and can thus compensate for the
manner in which microwave trips are recognized as valid trip
signals. In other words, microcontroller 108 can be adjusted to
require a certain number of microwave trips per each PIR trip
before recognizing occupancy of the monitored area.
[0046] Microcontroller 108 can be configured to include any
combination of the configurations described above for reducing
false trips. Alternatively, microcontroller 108 can be configured
to require detection of motion or occupancy by the microwave sensor
104 and by the PIR sensor 106 to maintain the lighting circuit in
the active state. In this type of arrangement, the microcontroller
108 thus performs an "AND" logic comparison of the detection result
from the PIR sensor signals and the detection result from the
microwave sensor signals to determine whether to continue to
control the relay drive circuit 126 to maintain the lighting
circuit in the active state to keep the lights in the monitored
area on.
[0047] That is, if the signals provided from analog circuitry 110
indicate that the PIR sensor 106 has detected PIR energy in the
occupied area but the signals provided from analog circuitry 114
indicate that the microwave sensor 104 has not detected a
sufficient level of reflected microwave signals, or vice versa,
microcontroller 108 will begin timing out the delay period. Unless
during the delay period the microwave sensor signals and the PIR
sensor signals indicate detection of motion or occupancy,
microcontroller 108 will control the relay drive circuit 126 to
drive the relay to place the in lighting circuit in the "inactive"
state once the delay period has elapsed. The lights will therefore
be shut off at the end of the delay period. However, if the
technology (PIR or microwave) failing to detect motion or occupancy
begins to detection motion or occupancy reasonably coincident with
the other technology before the delay period has elapsed, the
microcontroller 108 will reset its delay timer to zero and thus
maintain the lighting circuit in an active state to keep the lights
on. This arrangement allows for the sensitivities of the PIR and
microwave technologies to be increased to greater than initial
trigger mode levels to provide a larger area of coverage without
sacrificing low false trip performance.
[0048] Although only a few exemplary embodiments of this invention
have been described in detail above, those skilled in the art will
readily appreciate that many modifications are possible in the
exemplary embodiments without materially departing from the novel
teachings and advantages of this invention. Accordingly, all such
modifications are intended to be included within the scope of this
invention as defined in the following claims.
* * * * *